Place/spawn objects along curve with randomized scale and rotation?
Yes, use a particle system.



Use the techniques described in my answer to array a small plane ver a curve. Add an Array modifier set to fit curve and and a Curve modifier afterwards to a small plane or object that will be the base for ditributing your flowers.

Instead of Duplifaces as described in the answer add a new particle system to your plane object.

Turn on the option to Use Modifier Stack, emit from faces without Random and Even distribution. Then set Particles per face to 1 (if you desired a perfect single item alignement).

Under the Render Panel  of your particle system set it to either Object and pick your flower object or Group if you have a set different ones to distribute.

Turn on both Unborn and Died and turn off Emitter. You may also need to disable the physics set to None

You can now control the size randomness from the Random Size property under the Render panel.



Adjust particle count as necessary to match the number of arrayed items.